JPH02227116A - Composition for drying - Google Patents

Abstract

PURPOSE:To prevent liquefaction of deliquescent salts by sticking a powdery hydrophilic polymer to the coated layer of polyalkylene glycol dialkylester provided on the surfaces of the particles of deliquescent salts being a drying main agent. CONSTITUTION:The coated layer of polyalkylene glycol dialkylester is provided on the surfaces of the particles of deliquescent salts being a drying main agent. Then the composition for drying is prepared by sticking a powdery hydrophilic polymer to this coated layer. As the deliquescent salts, chloride of alkaline earth metals or alkali metals, e.g. calcium chloride and magnesium chloride, etc., are shown. As the utilized polyalkylene glycol dialkylester, a nonionic surfactant being a reactive product of polyethylene glycol having 2000-20000mol. wt. and 12-22C fatty acid is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a drying composition that prevents liquefaction of deliquescent salts as a main drying agent.

BACKGROUND OF THE INVENTION Deliquescent salts such as calcium chloride have long been used as desiccant agents because of their excellent hygroscopicity.

However, since such deliquescent salts liquefy as they absorb moisture, they are difficult to handle and have a limited range of use.

Therefore, various methods have been studied to prevent liquefaction without impairing the hygroscopic ability of deliquescent salts. For example, Japanese Patent Publication No. 60-28531 discloses that It has been proposed to use the polymers without melting or dissolving them, mechanically mixing them in powders or granules.

However, since this method simply mixes deliquescent salts and wood-philic polymers, it has the following drawbacks:
It was difficult to obtain a practical product.

+11 It is difficult to homogeneously mix deliquescent salts and hydrophilic polymers, both of which are powders or granules. In order to mix uniformly, it is necessary to granulate the wood-philic polymer to an appropriate size depending on the particle size of the deliquescent salt used.

(2) Even if the hydrophilic polymer is granulated to an appropriate size so that it can be mixed with the deliquescent salts, the deliquescent salts and the different hydrophilic polymer will easily separate, and the mixture will not be packaged. Separation begins during the transportation process until
It is difficult to ensure homogeneity of the final product.

(3) As a result of the above fil (21), there are large variations in the moisture absorption performance and gelling ability of the deliquescent liquid for each packaging unit, making it difficult to obtain a homogeneous product and increasing the risk of producing defective products.

Problems to be Solved by the Invention The present invention solves the drawbacks of such conventional methods, stably prevents liquefaction of deliquescent salts, and provides a method for handling with no variation in moisture absorption performance and gelling ability of deliquescent liquid. An object of the present invention is to provide a composition for easy drying.

Means for Solving the Problems The drying composition of the present invention provides a coating layer of polyalkylene glycol dialkyl ester on the surface of particles of deliquescent salts as a main drying agent, and adheres a powdery hydrophilic polymer to this coating layer. It is characterized by being

In the composition of the present invention, the powdery hydrophilic polymer is attached to the surface of the deliquescent salt particles via the polyalkylene glycol dialkyl ester, which has a binder effect and has excellent water absorption. Separation of gelling components is prevented, and a homogeneous and easy-to-handle product with excellent hygroscopicity and gelling ability of deliquescent liquid can be obtained.

In the present invention, the method for coating the surface of the deliquescent salt particles with the polyalkylene glycol dialkyl ester is not particularly limited, but generally, the polyalkylene glycol dialkyl ester is mixed with the deliquescent salt at a temperature equal to or higher than its melting point, and the particle surface is coated with the polyalkylene glycol dialkyl ester. It is preferable to spread the film on the film and then cool it to solidify it.

Polyalkylene glycol dialkyl ester itself has the ability to prevent deliquescent salts from liquefying as a component that absorbs water and gels, but at the same time, it has a moderate adhesive strength, so it can form additional gels with deliquescent salts. It also functions effectively as an adhesive to unite the components (powdered hydrophilic polymer), making it possible to provide a stable drying composition without directly exposing deliquescent salts to the atmosphere.

Such polyalkylene glycol dialkyl esters include polyethylene glycol having a molecular weight of 2,000 to 20,000 (preferably 5,000 to 10,000) and fatty acids having 12 to 22 carbon atoms (preferably 16 to 16 carbon atoms).
It is preferable to use a nonionic surfactant in which a hydrophobic group is bonded to both ends of a hydrophilic group obtained by reacting the surfactant with a fatty acid containing 18 as a main component.

These have the ability to gel 5 to 20 times their own weight of water and a 20x calcium chloride aqueous solution.

In addition, its melting point is approximately 40 to 70°C, and when mixed with deliquescent salt particles at temperatures above the melting point, a sticky coating layer is easily formed on the particle surface, and the powdered hydrophilic polymer is stably coated in this layer. can be attached.

Next, the deliquescent salts used in the present invention include alkaline earth metals or alkali metal chlorides, such as calcium chloride, magnesium chloride, lithium chloride, etc. alone or in mixtures. The most preferred salt is calcium chloride, which is highly hygroscopic and inexpensive, and both anhydrous and dihydrate forms of calcium chloride can be used.

The cheapest calcium chloride available is dihydrate, which has a particle size distribution of 1 to 4 ms+ and an average particle size of about 311.
m1, but the average particle size of calcium chloride is 1-
When the amount is less than 1, polyalkylene glycol dialkyl ester alone can provide a coating layer having the desired gelling ability, and a product with commercial value can be obtained. However, when the particle size becomes larger than that, it becomes difficult to obtain sufficient gelling ability with the polyalkylene glycol dialkyl ester layer alone.According to the present invention, the parent resin is added as an additional gelling component on the polyalkylene glycol dialkyl ester layer. Is it necessary to attach a polymer powder?

Powdered hydrophilic polymers attached to the surface of such deliquescent salts via a polyalkylene glycol dialkyl ester layer include polyacrylamide, cationized polyacrylamide, starch, and various modified starches (esterified starch, α (modified starch, cationized starch, etc.), polyvinyl alcohol, polyethylene oxide, methyl cellulose, cationized cellulose, etc. can be used.

Two or more of these may be used in combination.

In addition, in order to obtain a product with a high moisture absorption capacity, it is particularly preferable to use polyacrylamide, and when economic efficiency is important, it is preferable to use starch and various modified starches.

In the present invention, since the powdery wood-philic polymer is attached to the surface of the deliquescent salt through the polyalkylene glycol dialkyl ester layer, the particle size of the powder may be any size, but From the viewpoint of both properties and hygroscopic gelling performance, the smaller the size, the better, and it is generally best to use a powder in the form of a fine powder bundle.

Furthermore, calcium carbonate,
Inorganic powders such as zeolite, perlite, white carbon, etc. may also be used with wood-philic polymers.

In the present invention, in order to impart appropriate hygroscopic gelling ability to the desiccant composition and obtain good manufacturability, the ratio of calcium chloride to gelling components (polyalkylene glycol dialkyl ester and hydrophilic polymer) is It is necessary to adjust the ratio of the powder component (calcium chloride, wood-philic polymer, inorganic powder) and the binder component (polyalkylene glycol dialkyl ester) as appropriate.

The appropriate ratio of calcium chloride and gelling component varies depending on the performance of the gelling component, but calcium chloride (dihydrate)
The weight ratio of /gelling component (polyalkylene glycol dialkyl ester and hydrophilic polymer) is about 80/20 ~
80/14 can prevent liquefaction of deliquescent salts.

Points to consider when selecting and formulating gelling components are: ■ Absorption gelling ability of concentrated deliquescent liquid (CaC concentration 45χ to 40χ); ■ Gelling ability of dilute deliquescent liquid (CaC concentration 25χ to 15χ) of the car product. There are two points: the ability to prevent liquefaction when moisture absorption reaches a saturated amount, and it is necessary to select and formulate a gelling component to satisfy both of these points. In terms of performance, cationized polymer compounds such as cationized polyacrylamide, cationized starch, and cationized cellulose are particularly excellent, followed by polyacrylamide and polyalkylene glycol dialkyl ester, which exhibit excellent effects in that order. Note that the ability of other wood-loving polymers to gel a concentrated deliquescent liquid is at a considerably low level.

Next, ■ Regarding the gelling ability of dilute deliquescent liquid, the molecular weight of the gelling component is the main controlling factor, but the commonly available raw materials are listed in descending order of their ability: +11 polyacrylamide, polyethylene oxide,
Methyl cellulose, (2) starch, esterified starch, (3) cationized cellulose, polyalkylene glycol dialkyl ester, pregelatinized starch, (4) polyvinyl alcohol, cationized starch.

The utility value of polyacrylamide, which has excellent effects on both concentrated and dilute deliquescent liquids, is particularly great, but when considering the cost aspect, considering the characteristics of various gelling components, two or more types of parent trees can be used. It is preferable to use a mixture of suitable polymers.

The appropriate ratio of the powder component (calcium chloride, wood-philic polymer, inorganic salts) and binder component (polyalkylene glycol dialkyl ester) varies depending on the type of powder component, particle size, etc., but the weight ratio is approximately 80/20~9
376 is preferred.

Within this range, there are no problems such as residual unattached powder, blocking of product particles, or adhesion to the mixing pot, and it is possible to manufacture products of good quality.

If the binder component is too large, the product powder tends to form blocks and stick to the mixing pot, while if it is too small, unattached powder will remain, resulting in poor heat sealability due to powder dusting during product packaging. Problems are likely to occur.

When the particle size of calcium chloride and other powders is large, the appropriate amount of binder is relatively small compared to when the particle size is small.

Examples 1 to 6 Dry compositions were produced according to the formulations shown in Table 1 in the following manner. As a production pot, 31 is capable of heating and cooling.
It was manufactured using a ribbon mixer with a total amount of 1500 g.

+11 Calcium chloride was charged, and while heating and stirring, (2) polyalkylene glycol dialkyl ester was added, and after heating and stirring at 60 to 70°C for 10 minutes, (3) powdered wood-philic polymer was added, and 60 to 7
Heat and stir at 0°C for 5 minutes. When using one or more wood-loving polymers, they were added according to the order of the prescription, but the order of addition is not particularly limited. However, inorganic powders such as calcium carbonate may be used in combination. In this case, it is preferable to add this a-free powder last.
) Thereafter, the mixture is stirred and cooled to 45 to 50°C, and the product is taken out.

In all cases, stable granular products free of fine powder were obtained with a yield of 99% or more.

The saturated moisture absorption amount of each product at 25° C. and 85% RH is as follows.

Example 1 160% Example 2 183% Example 3 169% Example 4 170% Example 5 170% Example 6 236% All products are in a mochi-like gel state at saturated moisture absorption and exhibit good liquefaction prevention effects. Met.

In addition, there was no syneresis until saturated moisture absorption was reached, and a stable state was maintained over time.

Comparative Example Granular Calcium Chloride 120 same as used in Example 3
0g and scaly pregelatinized starch (particle size 0.5-3mm) 300
After mixing g for 10 minutes in a 31 ribbon mixer and pouring it out from the pot into a receiver, 10 samples were arbitrarily collected, and the same procedure was performed as in the 10 samples collected after the production of Example 3. I would like to compare the saturated moisture absorption amount and gel properties (temperature 25°C, humidity 85χ).

The results are shown in Table 2.

As is clear from the results in Table 2, in Example 3 of the present invention, a product with very uniform performance was obtained, whereas in the comparative example in which a deliquescent salt and a hydrophilic polymer were simply mixed,
Products with inconsistent quality were obtained, and it was observed that some defective products were produced because deliquescence could not be sufficiently prevented. Furthermore, in the comparative example, since the deliquescent salts and the hydrophilic polymer were both present in powder form, they were difficult to handle, and there were also problems such as poor sealability of the plastic bag due to dust.

Effects of the Invention Since the desiccant composition of the present invention coats the surface of deliquescent salts with a gelling component, liquefaction of deliquescent salts is stably prevented, and moisture absorption performance and gelling ability of deliquescent liquids are improved. In both cases, the product is good, consistent, and extremely easy to handle. There is no risk of powder falling during packaging or poor sealing of the plastic bag, and products with stable quality can always be obtained.

Patent applicant Dai-Kogyo Seiyaku Co., Ltd.

Claims (1)

[Claims] (1) A drying composition characterized in that a coating layer of polyalkylene glycol dialkyl ester is provided on the particle surface of a deliquescent salt as a main drying ingredient, and a powdery hydrophilic polymer is attached to this coating layer.